1. Field of the Invention
The invention relates to polymerized dicarboxylic acids and more particularly relates to the dimers of unsaturated dicarboxylic acids containing 16, 17, 18, 20, and 22 carbon atoms.
2. Brief Description of the Prior Art
It is well known that monomeric unsaturated fatty acids which are derived from natural sources are capable of being polymerized to the dimerized and trimerized form. This is usually realized by heating such unsaturated fatty acids in the presence of catalytic proportions of a mineral clay and, preferably, an acid-treated mineral clay, at temperatures in excess of about 180.degree. C. in an aqueous environment under autogenous pressure. Representative of the prior art teachings are those found in the U.S. Pat. Nos. 2,793,219 and 2,793,220.
We have now discovered that unsaturated dicarboxylic acids having 16, 17, 18, 20, or 22 carbon atoms, will also dimerize under the influence of clay catalysts to yield novel tetracarboxylic acids of 32, 34, 36, 40, or 44 carbon atoms having unique and useful properties. This is unexpected in view of the fact that a commercial unsaturated dicarboxylic acid of 21 carbon atoms will not dimerize under the same conditions.